I've implemented the G.711 mu-Law decompression to restore the recorded audio stream to 13 bit Wav uncompressed format. This works fine for the speech I'm working with. Now I need to get hold of the DTMF tones in the recorded audio stream.I'm using Vonage's system which sends an email with a voice message. The email has an attachment of the wav file of the speech. (8-bit 8kHz Mono) but something is happening to the DTMF tones generated by the buttons, it comes through as a noise. There is an encoding method (RFC2833) but I have not fathomed it yet.I would like to know:-Does Vonage really eat the tones and replace them with a noise?

Many voice mail systems don't allow DTMF tones in their recordings. Not sure if Vonage's is one of them, but the reasoning behind this is that the DTMF tones recorded in the message will be re-interpreted by the voice mail system as commands when they're played back.